Semiconductor circuit

ABSTRACT

An integrated semiconductor circuit arrangement composed of a substrate with an electrical portion, configured, for example, of an integrated circuit in planar CMOS or bipolar technology, an optical connecting layer disposed thereabove which includes at least one integrated (connecting) light waveguide, and an electro-optical and/or opto-electrical transducer disposed in a recess in the substrate, electrically connected to the integrated circuit and opticallly coupled to the light waveguide.

REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Federal Republic of Germanyapplication Ser. No. P 38 34 335.5 filed Oct. 10th, 1988, which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor circuit arrangement ofthe type including a substrate having at least one integrated circuitdisposed at a major surface of the substrate and a plurality ofelectrical conductor paths disposed on the major surface for providingelectrical connections to the integrated circuit.

Integrated semiconductor circuits are composed of a (semiconductor)substrate, e.g. wafer-shaped, monocrystalline silicon, having athickness of about 0.3 mm. A semiconductor circuit arrangement,composed, for example, of transistors and diodes, is formed on onesurface side of the substrate in presently customary semiconductortechnology, e.g. in the bipolar or CMOS (complementary metal oxidesemiconductor) technology. On this semiconductor circuit arrangement,there is disposed a conductor path layer composed, for example, ofaluminum conductor paths. The conductor path layer serves toelectrically connect the exemplary mentioned transistors and/or diodes.Such an arrangement is also referred to as an integrated circuit (IC).

Complex circuit arrangements, such as, for example, signal processors orcomputers, are generally composed of a larger number of such integratedcircuits. These integrated circuits are fastened, for example by gluingand/or soldering, to cards composed, for example, of ceramic or asemiconductor material, e.g. silicon. Electrical connections areestablished between the integrated circuits via electrical conductorpaths disposed on the card. In a conventional manner, these cards arethen pushed into a housing and are connected with one another viafurther electrical conductor paths in the rear wall of the housing.

The then required number of electrical connecting lines may be extremelylarge. For example, a signal processor may contain more than 100integrated circuits which require many thousands of electricalconnecting lines. The clock pulse rates of present-day circuits lietypically at 20 MHz. To produce faster signal processors, clock pulserates of more than 100 MHz are required. However, with increasing clockpulse rates, the danger of annoying electrical crosstalk arises betweenparallel or intersecting lines. Thus the probability of a bit errorincreases.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a semiconductorcircuit of the above type which permits a high packing density ofelectronic components, which permits the attainment of a high datatransmission rate between remotely disposed components and/or componentgroups, which provides for the lowest possible error probability, andwhich can be produced economically and reliably.

The above object is generally achieved according to the presentinvention by a semiconductor circuit arrangement of the type including asubstrate having at least one integrated circuit disposed at a majorsurface of the substrate and a plurality of electrical conductor pathsdisposed on the major surface for providing electrical connections tosaid integrated circuit; and wherein: a recess is provided in the majorsurface of the substrate; one of an electro-optical and anopto-electrical transducer is disposed in the recess and extends to themajor surface and is electrically connected with the at least oneintegrated circuit via at least one of the conductor paths; an opticalconnecting layer containing at least one light waveguide is disposed onthe substrate above the plurality of conductor paths; and means areprovided for optically coupling the transducer to the at least one lightwaveguide.

According to a further feature of the invention the substrate isprovided with at least one further transducer and integrated circuitwhich are disposed in a further recess in the major surface of thesubstrate, and the transducers are coupled together via the lightwaveguide in the connecting layer. Moreover according to another featureof the invention two such circuit arrangements may be optically coupledtogether.

A first advantage of the invention is that integrated light waveguidesare employed particularly for the connection between electroniccomponent groups. These light waveguides permit a high data transmissionrate and can be produced with great precision, for example with the aidof photolithography and/or ion implantation.

A second advantage is that the electrical portion and the opticalportion of the semiconductor circuit can be manufactured and testedseparately. Thus optimum, and therefore economical and reliable,manufacturing processes can be selected for each portion.

A third advantage is that the electrical portion of the semiconductorcircuit requires almost no bonded connections so that this portion canbe produced in planar semiconductor technology.

The invention will be described below in greater detail for embodimentsthereof with reference to the schematic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of one embodiment of asemiconductor circuit according to the invention.

FIG. 2 is a schematic cross-sectional view of a further embodiment of asemiconductor circuit according to the invention.

FIG. 3 is a schematic sectional view showing a plurality ofsemiconductor circuits according to the invention which are opticallycoupled together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a substrate 1, e.g. a circular monocrystalline siliconwafer as presently customary in the semiconductor art, having athickness of about 0.3 mm to 0.5 mm and a diameter of about 150 mm. Onthe upper major surface of this substrate or wafer, there are disposedelectrical conductor paths 3 produced in the presently customary planartechnology. Conductor paths 3 are contained in a layer composedpreferably of two layers of metal striplines separated from one anotherby dielectric insulating layers disposed between them. According to thepresent invention at least one recess or indentation 6 is made in theupper major surface of substrate 1, for example by etching, to such adepth that at least one electro-optical and/or opto-electricaltransducer 7, 7' and at least one integrated circuit 9 can be disposedtherein, for example by gluing or soldering, in such a manner that theirrespective upper surfaces essentially form a plane with the majorsurface of the substrate and the lower surface of the layer of conductorpaths 3. Then it is possible to electrically connect transducers 7 and7' and the integrated circuit with the conductor path layer by way ofconductor paths 3. In the drawing figures, the numeral 7 identifies anopto-electrical transducer, e.g. a photodiode, and the numeral 7' anelectro-optical transducer, e.g. a laser diode.

Further components, for example an electrical multiplexer/demultiplexerand driver circuits for transducers 7 and 7' may be disposed in recess6. The upper surface of all of these components essentially form a planeand are electrically contacted by way of the layer of conductor paths 3.Above the conductor path layer, there is at least one optical connectinglayer 4, e.g. a glass plate having a thickness of about 0.3 mm to 2 mm.At least one light waveguide 5, which is produced preferably in anoptically integrated manner, for example with the aid of the presentlycustomary photolithographic methods and a subsequent ion exchangemethod, is disposed in this connecting layer 4. The core of lightwaveguide 5, which in this embodiment extends substantially parallel tothe major surface of the substrate, has, for example, a square crosssectional area, with side lengths of about 40 μm. However, connectinglayer 4 may also be made of plastic in which plastic light waveguidesare provided. Additionally included in the connecting layer 4 arenon-transparent and/or semi-transparent deflection mirrors 8 with whichtransducers 7 and 7' can be optically coupled to the light waveguide 5,for example with the aid of further deflection mirrors 8' disposed insubstrate 1 in an optical path between the transducer and the lightwaveguide. All of the deflection mirrors 8 and 8' are produced byphysical and/or chemical processes, e.g. by stamping, cutting, grinding,polishing and/or etching of the respective layer containing thedeflection mirrors. In the illustrated embodiment of the invention witha semiconductor material substrate 1, the deflection mirrors 8' is acrystallographic surface of the substrate.

Thereafter, deflection mirrors 8 and 8' may also be coated withoptically active layers, e.g. semi-transparent or totally reflectinglayers. This coating process may be effected, for example, in a vacuumwith the aid of an oblique vapor deposition process. Such an opticalconnecting layer 4 is then fastened on the conductor path layer 3 or aprotective layer, e.g. an oxide layer, thereabove, for example bygluing, so that deflection mirrors 8 face the conductor path layer andare disposed above the optical entrance and/or exit openings oftransducers 7 and 7'. It is understood that corresponding openings areprovided in the conductor path layer. Such an arrangement makes itpossible for the light 10 emanating from transducer 7', e.g. asemiconductor laser with such a modulation that a data transmission rateup to about 2 Gbit/s is possible, to be coupled into the light waveguide5 disposed in connecting layer 4 and can there be transmitted overrelatively long distances, e.g. several cm, as shown by the interruptionto the transducer 7 shown on the right in FIG. 1. The resultingelectrical signals are transmitted by way of electrical conductor paths3 to an integrated circuit 9, e.g. a demultiplexer, and are thenprocessed further.

Light waveguide 5 may have such dimensions, for example, that it ispossible to transmit in opposite directions in optical wavelengthmultiplex. This is indicated by the double arrows for the lighttraveling in the waveguide 5. It is also possible, for example, by wayof ion implantation, to also produce a further light waveguide 5' insubstrate 1 and to transmit light 10 through it. Moreover, at least onefurther optical connecting layer 4' containing at least one lightwaveguide 5' may also be provided below substrate 1.

If an electro-optical transducer 7' is employed which transmits lightperpendicularly to the surface of substrate 1, deflection mirror 8' maybe omitted and the transducer 7' position directly below the associateddeflection mirror 8 in a manner similar to that shown for theopto-electric transducer 7.

Moreover, an additional layer-type semiconductor circuit arrangement 2,for example in bipolar technology, may be provided in substrate I at itsmajor surface and connected to the conductor paths 3.

FIG. 2 shows a further embodiment of the invention in which thesubstrate is a composite formed of a lower substrate 1, which does nothave any recesses but preferably a planar upper surface, and an uppersubstrate 1' disposed on the upper surface of the lower substrate. Theelectrical conductor paths 3 are disposed on the upper major surface ofthe upper substrate 1', which is preferably composed of Si and isfastened to substrate 1, for example by soldering, welding, gluing,bonding or by an anodic bonding. The upper substrate 1' is provided withrecesses 6, which in this case are through bores, in which transducers 7and 7' and integrated circuits 9 are accommodated. The height of thesubstrate 1', and of the transducers 7 and 7' and the integratedcircuits 9 disposed in the recesses 6 of substrate 1' is the same, withpermissible deviations of no more than about 20 μm. In contrast to FIG.1, the electrical conductor paths 3 also do not extend over the entiresurface of integrated circuits 9 but only to the contact points in theedge regions.

Combinations of the embodiments of FIGS. 1 and 2 are also possible.

FIG. 3 shows an embodiment in which several arrangements according toFIG. 1 and/or FIG. 2 can be coupled optically. This is done with the aidof an optical circuit board 11, e.g. also a glass or plastic plate, inwhich there is disposed at least one light waveguide 5" andnon-transparent and/or semi-transparent deflection mirrors 8". Circuitboard 11 is arranged essentially perpendicular to several parallelarrangements of FIGS. 1 and 2 in such a manner that the deflectionmirrors 8" disposed in circuit board 11 couple the light 10 in lightwaveguide 5" into light waveguides 5 and/or 5'.

Another additional or alternative possibility for optical couplingsbetween several arrangements according to FIG. 1 is shown in the upperportion of FIG. 3. There, two semiconductor circuit arrangementsaccording to FIG. 1 are disposed adjacent and in parallel such thattheir respective optical connecting layers 4 face one another. Theselayers 4 may be spaced from one another, as shown, or may contact oneanother and/or may be connected, for example, by means of an adhesive.The light (arrows) emanating from a transducer 7' is coupled, forexample by way of an optical imaging arrangement 13 included in theconnecting layer, into a light path 12, for example another lightwaveguide, which extends perpendicularly through the two connectinglayers 4 and is provided at its other end with an opto-electricaltransducer 7, e.g. a photodiode.

It is further possible to place optical arrangement 13 in the edgeregion of the substrate and thus couple together several arrangementsaccording to FIGS. 1 and 2.

The described arrangements permit, in an advantageous manner, thecombination of the advantages of an integrated electrical circuit withthose of a integrated optical circuit. In this way, it is possible toproduce, for example, very fast high performance computers since, on theone hand, it is possible to give the electrical components a highpacking density and, on the other hand, a high data transmission ratebecomes possible between different circuit arrangements.

The present invention is not limited to the described embodiments butcan also be applied in the same sense in others. For example, theoptical connecting layers 4 may contain optical switches and/or opticalmultiplexers, and/or demultiplexers, and/or may be coupled with themand/or further individual light waveguides, e.g. a very long monomodelight waveguide.

The invention now being fully described, it will be apparent to one ofordinary skill in the art that any changes and modifications can be madethereto without departing from the spirit or scope of the invention asset forth herein.

WHAT IS CLAIMED:
 1. In a semiconductor circuit arrangement including asubstrate having at least one integrated circuit disposed at a majorsurface of the substrate and a plurality of electrical conductor pathsdisposed on said major surface for providing electrical connections tosaid at least one integrated circuit; the improvement comprising: arecess in said major surface of said substrate; said at least oneintegrated circuit and one of an electro-optical and an opto-electricaltransducer disposed in said recess and each extending to said majorsurface and with said transducer being electrically connected with saidat least one integrated circuit via at least one of said conductorpaths; an optical connecting layer containing at least one lightwaveguide disposed on said main surface of said substrate above saidplurality of conductor paths; and means for optically coupling saidtransducer to said at least one light waveguide.
 2. A semiconductorcircuit arrangement as defined in claim 1 wherein said transducer is anelectro-optical transducer; and further comprising: a further recessformed in said major surface of said substrate; a further integratedcircuit and an opto-electrical transducer disposed in said furtherrecess and each extending to said major surface, and with saidopto-electrical transducer and said further integrated circuit beingelectrically connected via at least one of said conductor paths; andmeans for optically coupling said opto-electrical transducer to said atleast one light waveguide whereby said transducers are optically coupledtogether via said at least one light waveguide.
 3. A semiconductorcircuit arrangement as defined in claim 1 wherein: said substrate isformed of semiconductor material; and a further integrated circuit isformed in said major surface of said substrate and electricallyconnected to said conductor paths.
 4. A semiconductor circuitarrangement as defined in claim 1 further comprising a further opticalconducting layer disposed on the opposite major surface of saidsubstrate and having at least one further light waveguide therein.
 5. Asemiconductor circuit arrangement as defined in claim 1 wherein said atleast one light waveguide extends perpendicular to said major surface.6. A semiconductor circuit arrangement as defined in claim 1 whereinsaid at least one light waveguide extends parallel to said majorsurface.
 7. A semiconductor circuit arrangement as defined in claim 6wherein said means for optically coupling includes at least onedeflection mirror provided in said optical connecting layer in a lightpath between said light waveguide and said transducer.
 8. Asemiconductor circuit arrangement as defined in claim 7 wherein saidtransducer is an electro-optic semiconductor transducer which emitslight essentially parallel to said major surface of said substrate; andsaid coupling means includes a further deflection mirror disposed in arecess in said surface of said substrate and in said light path betweensaid transducer and said light waveguide.
 9. A semiconductor circuitarrangement as defined in claim 8 wherein: said substrate is formed ofsemiconductor material, and said at least one deflection mirror disposedin said substrate is a crystallographic surface of said substrate.
 10. Asemiconductor circuit arrangement as defined in claim 7 wherein saidtransducer is an electro-optic semiconductor transducer which emitslight essentially perpendicularly to said major surface of saidsubstrate.
 11. A semiconductor circuit arrangement as defined in claim 7wherein: said optical connecting layer is composed of one of glass andplastic; and said deflection mirror disposed in said connecting layer isa surface thereof produced by physical or chemical treatments.
 12. Acomposite semiconductor circuit arrangement including a plurality ofsemiconductor circuit arrangements as defined in claim 1, with said atleast one light waveguide in said connecting layers of said plurality ofsemiconductor circuit arrangements extending parallel to the respectivesaid major surfaces; an optical circuit board including at least onelight waveguide disposed perpendicular to said major surfaces of saidplurality of semiconductor circuit arrangements adjacent an end thereof;and means for optically coupling said light waveguide of said opticalcircuit board to the respective said light waveguides of said pluralityof semiconductor circuit arrangements to optically couple together atleast two of said semiconductor circuit arrangements.
 13. A compositesemiconductor circuit arrangement as defined in claim 12 wherein saidoptical circuit board is composed of one of glass, plastic, asemiconductor material and a combination of these materials.
 14. Acomposite semiconductor circuit arrangement including: two ofsemiconductor circuit arrangements as defined in claim 1 with said atleast one light waveguide in said optical connecting layer of each ofsaid two semiconductor circuit arrangements extending perpendicular tothe respective said major surface, said two semiconductor circuitarrangements being disposed with their respective said opticalconnecting layers adjacent one another and with the respective saidlight waveguides aligned; and said means for optically coupling includesan optical imaging arrangement disposed in the resulting light path. 15.A composite semiconductor circuit arrangement as defined in claim 14wherein said optical imaging arrangement is configured as an integratedoptical arrangement formed in said connecting layer.